The present invention relates generally to linear position sensors.
Modern motor vehicles are equipped with numerous sensors that enhance the safety and quality of the vehicle operation. Among these sensors are linear position sensors that are used to determine linear motion of a moving part, e.g., a throttle, a gas pedal, a brake pedal, and a clutch pedal, relative to the vehicle chassis.
Magnetic position sensors are advantageous for this type of application because they do not necessitate contact between the moving parts. Most conventional magnetic sensors are linear over a very small range. Sensor assemblies that are useful over larger ranges typically require a magnetic sensor that is as long as the range required and as such, that increases the cost of the sensor assembly. Other magnetic sensors that utilize a moving magnet have demonstrated linearity over relatively large ranges, but the moving magnet must be incorporated into the moving part, which can be quite complicated.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A linear position sensor assembly includes a mobile target and a stationary magnet that has a magnetic field that generates a magnetic flux density around the target. The magnet is spaced from the target and a magnetic sensor is placed adjacent to the magnet. The sensor senses changes in the magnetic flux density as the target moves relative to the magnet and outputs a linear signal representing changes in the magnetic flux density. Preferably, the magnetic sensor is a Hall effect sensor, a semiconductor magnetoresistor, a permalloy magnetoresistor, or a giant magnetoresistor. If a Hall sensor or a semiconductor magnetoresistor is used, it senses a component of the flux density which is normal to its surface. On the other hand, if a permalloy magnetoresistor or a giant magnetoresistor is used, it senses the component of flux density which is co-planar, or parallel, to its surface.
In one aspect of the present invention, the magnet defines a bottom and the magnetic sensor is placed adjacent to the bottom of the magnet. The target defines a direction of motion and the magnet is oriented so that the magnetic field is perpendicular the direction of motion of the target. In this aspect, the target forms a slot that changes the magnetic flux density sensed by the magnetic sensor as the target moves. Moreover, the slot defines a length and the signal output by the magnetic sensor is linear over a range between one to two millimeters (1 mm-2 mm) smaller than the length of the slot.
In another aspect of the present invention, the magnet defines a bottom and the magnetic sensor is placed adjacent to the bottom of the magnet. In this aspect of the present invention, the target defines a direction of motion and the magnet is oriented so that the magnetic field is parallel to the direction of motion. Moreover, the target defines a length and the signal output by the magnetic sensor is linear over a range between one to two millimeters (1 mm-2 mm) smaller than the length of the target.
In yet another aspect of the present invention, the magnet defines a side and the magnetic sensor is placed adjacent to the side of the magnet. In this aspect, the target defines a direction of motion and the magnet is oriented so that the magnetic field is perpendicular to the direction of motion. Furthermore, the magnet defines a length and the target defines a length. And, the signal output by the magnetic sensor is linear over a range between one to two millimeters (1 mm-2 mm) smaller than the length of the target or the length of the magnet, whichever is smaller.
In still another aspect of the present invention, the magnet defines a side and the magnetic sensor is placed adjacent to the side of the magnet. Moreover, the target defines a direction of motion and the magnet is oriented so that the magnetic field is parallel to the direction of motion. In this aspect of the present invention, the target forms a slot that changes the magnetic flux density sensed by the magnetic sensor as the target moves. Also, the magnet defines a length and the slot defines a length. The signal output by the magnetic sensor is linear over a range between one to two millimeters (1 mm-2 mm) smaller than the length of the slot or the length of the magnet, whichever is smaller.
In yet still another aspect of the present invention, a method for linearly determining the position of a moving part relative to a stationary part includes establishing a target on the moving part. Then, a magnetic sensor is disposed on or adjacent to the stationary part. A stationary magnet is disposed on or adjacent to the stationary part. In this aspect of the present invention, the magnet defines a magnetic field that permeates the magnetic sensor. Moreover, the magnetic sensor senses changes in magnetic flux density as the target moves relative to the stationary magnet.
In another aspect of the present invention, a linear position sensor assembly includes a stationary part and a moving part that moves linearly with respect to the stationary part. The sensor assembly also includes means for generating a magnetic field that emanates from the stationary part, means established by the moving part for causing changes in magnetic flux density of the magnetic field, and means for sensing changes in the magnetic flux density and outputting a linear signal representing changes in the magnetic flux density.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: